Apparatus and method for wrapping and sealing cylindrical packages with a stretch film material

Abstract

A cylindrical package to be wrapped with stretch film sheet material is supported on a pair of parallel, horizontally spaced, horizontally extending support rollers, one of which is rotatably driven and the other of which is a slave roll which rotates idly. A stretch film supply means is mounted on a movable carriage with the axis of the film supply means parallel to the axis of rotation of the package. The carriage is caused to reciprocate along a path parallel to the axis of rotation of the package and the support rollers. The reciprocation occurs between a first position where the film material extends beyond one end of the package a distance at least as great as the radius of the package and a second position where the film extends beyond the other end of the package a similar distance. The film material is wrapped while tension is applied thereto. The tensioning device is designed to vary pressure at the end portions of the carriage path in relationship to the intermediate portions, so that the overlapped portion of the stretch film material tends to fold in and seal the ends of the package. A post member extends across and adjacent to each end of the package to ensure folding in and sealing of the film material.

What is claimed is: 
     
       1. A method of wrapping the periphery and sealing the ends of cylindrical packages with stretch film comprising the steps of: (a) supporting the cylindrical package with the longitudinal axis horizontally oriented;   (b) rotating said package by applying a driving force against the side surface thereof;   (c) applying the free end of a sheet of stretch film material delivered from a supply means of such material to the side surface of said package as said package is turning;   (d) as rotation of said package continues, moving said supply means of film material back and forth in a horizontal path parallel to the axis of rotation of said package from a first position in which said film overlaps one end of said package a distance greater than the radius of said package and a second position in which said film overlaps the other end of said package a distance greater than the radius of said package, while applying tension to said film to stretch it as it is wrapped on the package, and automatically applying varied tension to said film such that a prescribed tension is applied at the ends of the path to turn said film toward said longitudinal axis of the article to thereby cover the ends of the article, and automatically applying a different tension during the wrapping of the package in the intermediate portion of the path.   
     
     
       2. The method according to claim 1 wherein said tension is varied with greater tension being applied at the ends of the path than during the wrapping of the package in the intermediate portion of the path. 
     
     
       3. The method according to claim 1 wherein said tension is varied with lesser tension being applied at the ends of the path than during the wrapping of the package in the intermediate portion of the path. 
     
     
       4. Apparatus for wrapping the peripheral surface and sealing the ends of cylindrical packages with stretch film comprising: (a) a pair of rotatable support rollers horizontally spaced apart a distance less than the diameter of said cylindrical packages whereby said packages may be laid on and supported by said rollers;   (b) drive means associated with said apparatus for rotating said packages, when mounted, at a predetermined rate;   (c) means for rotatably supporting a supply means of stretch film material adjacent said support rolls, the longitudinal axis of said supply means of sheet material being substantially parallel to the longitudinal axis of said cylindrical package when positioned on said support rollers;   (d) means for causing relative movement between said package and said supply means of stretch film material along a path parallel to the longitudinal axis of said cylindrical package from a first position where said stretch film overlaps one end of said cylindrical package a distance greater than the radius of said package, and a second position where said film overlaps the other end of said cylindrical package a distance greater than the radius of said package; and   (e) tensioning means associated with said supply means for applying a prescribed variable tension on said film to stretch it as it is wrapped onto said cylindrical package;   (f) activating means to control the tensioning means to automatically apply a prescribed force at said first and second positions to turn said film toward said longitudinal axis of the article to thereby cover said ends of the article, and to automatically apply a different force at points therebetween during the wrapping operation of cylindrical package.   
     
     
       5. The apparatus according to claim 4 wherein said drive means includes a drive roll mounted for rotation and having the periphery thereof engagable with the periphery of at least one of said support rollers, motor means for causing rotational motion of said drive roll which is transmitted to the support roller engaging said drive roll. 
     
     
       6. The apparatus according to claim 4 wherein said means for rotatably supporting said supply means comprises a carriage mounted beneath and between support rolls. 
     
     
       7. The apparatus according to claim 6 wherein said carriage includes a rectangular frame having sides and ends, a bearing plate extending upwardly from opposite ends of said frame on which said supply means is rotatably mounted. 
     
     
       8. The apparatus according to claim 6 wherein said means for causing relative movement between said package and said supply means comprises a plurality of wheels attached to and extending outwardly from opposite sides of said carriage, a pair of tracks or rails associated with said apparatus and extending in spaced parallel relation to each other and parallel to the longitudinal axis of said cylindrical package, said carriage being supported on said pair of rails by said wheels, and said activating means comprises means for causing reciprocal movement of said carriage back and forth along said path between said first and second positions. 
     
     
       9. The apparatus according to claim 8 wherein said means for causing reciprocal movement of said carriage comprises a threaded rod extending parallel to and between said rails, a threaded opening through said carriage corresponding to the threads on said threaded rod and receiving said threaded rod, a reversible motor means attached to said threaded rod for rotation thereof, whereby rotation of said threaded rod causes a movement of said carriage along said path. 
     
     
       10. The apparatus according to claim 8 wherein said activating means comprises a sensing means for determining the pressure of said carriage at each of first and second positions. 
     
     
       11. The apparatus according to claim 4 wherein said tensioning means comprises a brake device in engagement with the film on said supply means. 
     
     
       12. The apparatus according to claim 11 wherein said brake engages the film on said supply means with greater force at said first and second position than at points therebetween. 
     
     
       13. The apparatus according to claim 11 wherein said brake engages the film on said supply means with lesser force at said first and second position than at points therebetween. 
     
     
       14. The apparatus according to claim 4 wherein a post is attached to said apparatus adjacent each end of said package in confronting relation thereto and in engagement with the edge portion of said package being wrapped, but slightly spaced from the ends of said package near the axis of rotation, said post extending past the axis of revolution whereby said end sealing is ensured by the electrostatic attraction of said film toward the axis of said package as exerted by the free end of said post and the pressing of the post against the overlapped portion of said film. 
     
     
       15. The apparatus according to claim 14 wherein said posts are adjustably attached to said apparatus for repositioning thereof depending on the length of said package being wrapped.